Human gender differences in immune reactivity have been studied at two levels.
Ahmed et al. (1985) have reviewed proximate mechanisms in sex hormone actions
that explain, in part, the superior immoral and cell-mediated immunity of females,
their greater resistance to infection and correlated greater longevity, as well
as greater incidence of autoimmune diseases. The ultimate mechanisms that led
to the evolution of this difference has been the subject of growing interest
and debate. In explaining how these differences have evolved, researchers have
overlooked an important group that could help shed light on the debate: non-human
primates, specifically the lesser and great apes. In an effort to address this
question, a preliminary study was conducted of ape gender differences in mortality
by gathering data from literature, recent ape studbooks (including the 1990
North American Chimpanzee Regional Studbook the 1993 International Studbook
of the Bonobo, the 1995 International Studbook of the Orangutan, the 1993 White-handed
Gibbon Studbook and the 1994 Western Lowland Gorilla Studbook) and a request
for death records from certain North American zoos and breeding facilities.
Much well-established heterogeneity was found in the sex-ratios of infant mortality,
percent of deaths caused by infection and average age at death. The heterogeneity
fell out at the species level and followed little phylogenetic patterns. Chimps,
orangutans, gorillas and gibbons seem to follow predictions of lesser female
infant mortality while Bonobos showed equal or slightly higher female infant
mortality. Infectious organisms were associated with proportionately greater
Gibbon, Gorilla, Bonobo and Orangutan female deaths, contrary to expectations.
Too few chimp records were received to make an accurate assessment. While some
of these deviations may be due to sample size, robust differences exist that
require explanation. In an effort to better understand the phenomena, the scope
of the study needs to be expanded and sample sizes increased by making an open
call to zoos, primate facilities and private collections interested in participating.
Letter of Gratitude
